1. Field of the Invention
This invention relates to a method of controlling the position of a pickup. More particularly, the invention relates to a pickup position control method for a disk player in which, when the power supply is interrupted during reproduction, the pickup is held at the last reading position.
2. Background of the Prior Art
Compared with other types of disk players for reproducing signals recorded on disk-shaped recording media such as digital audio disks (hereinafter referred to merely as "disks"), a mobile disk player or a portable disk player has an increased chance that the power supply is interrupted during reproduction. When the power supply is interrupted in this manner, a problem lies in determining the point on the disk from which the reproduction is started again when the electric power is once again supplied to the disk player.
As a solution of the problem, a disk player has been proposed in the art in which, when the power supply is interrupted during reproduction, the address data of the last reading position is obtained from the data which has been read by the pickup prior to interruption of the power supply. This address data is stored in a backup memory and the pickup is returned to its home position upon power interruption. When the electric power is supplied to the disk player again, the address data of the last reading position is read out of the backup memory and the pickup is moved to the address position thus read out. The reproduction is restarted from that position.
The conventional disk player described above is disadvantageous in that it is relatively high in manufacturing cost because it is necessary to use the backup memory.
The use of the backup memory has been eliminated by another disk player in which, when the power supply is interrupted during reproduction, the pickup is held mechanically at the last reading position. When the electric power is supplied to the disk player again, the reproduction is started from the last reading position.
If a disk which is eccentric is played by the disk player in which the pickup is held mechanically at the last reading position, then for the eccentricity, the spot light (data reading point) of the pickup is driven radially of the disk by the actuator of the pickup to follow a predetermined track. However, if the power supply is interrupted during the track following operation, the actuator is returned to the neutral position, as a result of which a difference corresponding to the eccentricity can exist between the position where the pickup is mechanically held and the last reading position of the spot light. In other words, if the disk is eccentric, then the accuracy of holding the pickup in place is substantially limited by the eccentricity of the disk.
According to the disk standard, the eccentricity of a disk is .+-.0.2 mm, which is about 27 to 77 sec. in terms of reproduction address time. Because of this great fluctuation, when the electric power is supplied to the disk player after the interruption of the power supply, the reproduction cannot be started from the last reading position.
Furthermore, a problem occurs, not only in the disk player of the type that the address data of the last reading position is stored in the backup memory but also in the disk player of the type that the pickup is held mechanically at the last reading position. When the electric power is supplied to the disk player again, the reproduction is started from the last reading position, i.e., the music is reproduced a second time from the last reading position. Therefore, the person perceives the reproduced music to be unnatural.